One-pot synthesis of 1,4-diarylnaphthalenes via a Wittig-Horner reaction/[4+2] cycloaddition/dehydrogenation sequence

Article abstract of DOI:10.1055/s-0028-1083356

A one-pot synthesis of 1,4-diarylnaphthalenes from cinnamaldehydes, dimethyl benzylphosphonates, and benzenediazonium-2-carboxylate is described. The tandem process involves the Wittig-Horner reaction of the cinnamaldehyde with the benzylphosphonate, [4+2

Full text of DOI:10.1055/s-0028-1083356

PAPER
1075
One-Pot Synthesis of 1,4-Diarylnaphthalenes via a Wittig–Horner Reaction/
[4+2] Cycloaddition/Dehydrogenation Sequence
O
ne-Pot Synthe
h
sis of 1,4-D
i
e
arylnaphtha
n
lene
s
gbo Chen, Wangge Shou, Yanguang Wang*
Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. of China
Fax +86(571)87951512; E-mail: orgwyg@zju.edu.cn
Received 14 October 2008; revised 25 November 2008
pated that the Wittig–Horner reaction of 2a and 3a would
Abstract: A one-pot synthesis of 1,4-diarylnaphthalenes from cin-
namaldehydes, dimethyl benzylphosphonates, and benzenediazoni-
um-2-carboxylate is described. The tandem process involves the
Wittig–Horner reaction of the cinnamaldehyde with the ben-
result in the diene 5, which would subsequently react with
the in situ generated benzyne via a tandem [4+2]
cycloaddition11a and dehydrogenation process to afford
zylphosphonate, [4+2] cycloaddition of the thus-formed diene with 1,4-diphenylnaphthalene (4a) (Scheme 1). We found that
benzyne, and subsequent dehydrogenation. The procedure is gener-
al and efficient and the substrates are readily available.
2a reacted with 3a in the presence of excess potassium
tert-butoxide (2.6 equiv) in anhydrous tetrahydrofuran,
Key words: diphenylnaphthalene, tandem reaction, Wittig–Horner
reaction, cycloaddition, benzyne
followed by treatment with excess 1 (2.5 equiv) in 1,2-
dichloroethane at 65–75 °C to give the desired product 4a
in 63% isolated yield (Table 1, entry 1).
–
CO2
Substituted naphthalenes are very important building
blocks for the synthesis of pharmaceuticals1 and polycy-
clic aromatic materials.2 Traditionally, the regioselective
construction of substituted naphthalenes has been carried
out by the stepwise introduction of substituents through
electrophilic substitution.3 More modern achievements in
the regioselective construction of substituted naphtha-
lenes include annulation of benzene molecules bearing an
unsaturated carbonyl side chain,4 cross-coupling reactions
of naphthalenes5a or halonaphthalenes,5b,c reactions of aryl
halides with alkynes,6 cyclization of alkynes and ben-
zynes,7 annulations via Fisher carbenes,8 and the coupling
of alkynes with arylacetaldehydes or aryl epoxides.9 How-
ever, these methods involve either expensive transition
metal catalysts or multistep procedures. In some cases, the
reactions produce mixtures of isomers.
+
N2
1
Figure 1
O
Ph
Ph
Ph
2a
+
1. t-BuOK
2. 1 (2.5 equiv)
(MeO)2OP
Ph
4a
3a
Wittig–
Horner
reaction
Benzynes are highly reactive intermediates that have
found numerous applications in organic synthesis.10 The
dienophilic nature of the benzynes have been exploited in
[2+2] and [4+2] cycloaddition reactions.11 Benzenediazo-
nium-2-carboxylate (1) is a benzyne precursor (Figure 1)
that is easily prepared from anthranilic acid.12 Previously,
we reported a tandem reaction of aromatic aldehydes and
anilines with benzyne generated in situ from 1 for the
preparation of 6-arylphenanthridines.13 In connection
with this work, we herein report a one-pot tandem ap-
proach to 1,4-diarylnaphthalenes from benzenediazoni-
um-2-carboxylate, cinnamaldehydes, and dimethyl
benzylphosphonates.
Ph
H
Ph
H
Ph
Ph
[4+2]
cycloaddition
5
6
Scheme 1 Synthesis of 1,4-diphenylnaphthalene (4a)
With this result in hand, we went on to study the scope of
the methodology. Using the established reaction condi-
tions, a variety of cinnamaldehydes 2 and dimethyl
benzylphosphonates 3 were investigated. As shown in
Table 1, all of the reactions generated the desired 1,4-di-
arylnaphthalenes 4. The yields of the isolated products
ranged from 55–85%. The benzylphosphonates substitut-
ed with strongly electron-donating groups (Table 1, en-
tries 3, 7, 11, 16, and 21) gave higher yields than those
with strongly electron-withdrawing groups (Table 1, en-
tries 5 and 13). The products were characterized by IR, 1H
NMR, 13C NMR, MS, and HRMS spectra.
In our initial experiments, we examined the model reac-
tion using 1 as the benzyne precursor, cinnamaldehyde
(2a), and dimethyl benzylphosphonate (3a). It was antici-
SYNTHESIS 2009, No. 7, pp 1075–1080
x
x
.
x
x
.2
0
0
9
Advanced online publication: 11.02.2009
DOI: 10.1055/s-0028-1083356; Art ID: F21708SS
© Georg Thieme Verlag Stuttgart · New York

1076
Z. Chen et al.
PAPER
PO(OMe)2
OMe
1. t-BuOK, THF
r.t., 4 h
O
OMe
+
2. 1 (1.2 equiv)
70–75 °C, 3 h
2c
3a
7 85%
Scheme 2 Synthesis of the 1,4-dihydronaphthalene intermediate 7
Table 1 One-Pot Synthesis of Substituted 1,4-Diarylnaphthalenes 4a
R2
R2
PO(OMe)2 1. t-BuOK, THF
r.t., 3–5 h
O
+
R3
R1
2. 1 (2.5 equiv)
R3
R1
DCE
65–75 °C, 3 h
2
3
4
Entry
1
R1
H
H
H
H
H
H
H
H
R2
H
R3
Product
4a
4b
4c
Yieldb (%)
63
H
2
H
3-Me
4-MeO
4-Br
4-NO2
H
64
3
H
73
4
H
4d
4e
61
5
H
55
6
Me
Me
Me
4f
69
7
4-MeO
4-Br
H
4g
4h
4c
75
8
68
9
4-MeO
4-MeO
4-MeO
4-MeO
4-MeO
2-MeO
2-MeO
2-MeO
2-MeO
2-Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
72
10
11
12
13
14
15
16
17
18
19
20
21
22
3-Me
4-MeO
4-Br
4-NO2
H
4i
78
4j
82
4k
4l
70
60
4m
4n
4o
4p
4q
4r
79
3-Me
4-MeO
4-Br
H
76
85
73
68
2-Me
4-Br
3-Me
4-MeO
4-Br
65
2-Cl
4s
66
2-Cl
4t
74
2-Cl
4u
70
a Reaction conditions: (1) 2 (5 mmol), 3 (5 mmol), t-BuOK (13 mmol), THF (45 mL), r.t., 3–5 h; (2) 1 (12.5 mmol), DCE (60 mL), 65–75 °C, 3 h.
b Isolated yield.
We obtained the 1,4-dihydronaphthalene intermediate 7 This result supports the proposed mechanism as shown in
as a mixture of cis- and trans-isomers by using 1.2 equiv- Scheme 1.
alents of benzyne to perform the reaction (Scheme 2).
Synthesis 2009, No. 7, 1075–1080 © Thieme Stuttgart · New York

PAPER
One-Pot Synthesis of 1,4-Diarylnaphthalenes
1077
13C NMR (125 MHz, CDCl3): d = 159.2, 141.1, 139.8, 139.7, 133.4,
132.4, 132.2, 131.4, 130.4, 128.5, 127.5, 126.74, 126.70, 126.68,
126.62, 126.04, 126.01, 114.0, 55.6.
MS (EI): m/z (%) = 310 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H18O: 310.1358; found:
In conclusion, we have developed a one-pot synthesis of
1,4-diarylnaphthalenes from cinnamaldehydes, dimethyl
benzylphosphonates, and benzenediazonium-2-carboxy-
late. The tandem process involves the Wittig–Horner re-
action of cinnamaldehyde with benzylphosphonate, [4+2]
cycloaddition of the thus formed diene with benzyne, and
subsequent dehydrogenation. The procedure is general
and efficient and the substrates are readily available. Con-
sidering the importance of naphthalene derivatives, this
method should find wide application in the synthesis of
polycyclic aromatic hydrocarbons.
310.1351.
1-(4-Bromophenyl)-4-phenylnaphthalene (4d)
White solid; mp 118–119 °C.
IR (KBr): 1586, 1490, 1443, 1382, 1170 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.01–7.99 (m, 1 H), 7.94–7.92 (m,
1 H), 7.68–7.66 (m, 2 H), 7.57–7.52 (m, 4 H), 7.50–7.42 (m, 7 H).
13C NMR (125 MHz, CDCl3): d = 140.9, 140.5, 140.0, 138.7, 132.2,
132.0, 131.9, 131.7, 130.3, 128.6, 127.6, 126.8, 126.7, 126.34,
126.26, 121.8.
MS (EI): m/z (%) = 358 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C22H15Br: 358.0357; found:
IR spectra were obtained on a FT-IR spectrophotometer. NMR
spectra were recorded for 1H NMR at 500 MHz, for 13C NMR at 125
MHz. For 1H NMR, TMS served as internal standard (d = 0 ppm).
For 13C NMR, CDCl3 was used as internal standard (d = 77.25 ppm)
and spectra were obtained with complete proton decoupling.
LR-MS and HRMS were obtained using EI ionization. Melting
points were measured with micro melting point apparatus.
358.0359.
1-(4-Nitrophenyl)-4-phenylnaphthalene (4e)
Yellow solid; mp 160–161 °C.
1,4-Diarylnaphthalenes 4; General Procedure
Cinnamaldehyde 2 (5 mmol) and dimethyl benzylphosphonate 3 (5
mmol) were dissolved in anhyd THF (20 mL). The resulting soln
was added dropwise slowly to t-BuOK (13 mmol) in anhyd THF (25
mL) at 0 °C, the mixture was stirred at r.t. for 3–5 h. To the mixture
was added a suspension of benzenediazonium-2-carboxylate (1,
12.5 mmol) in DCE (60 mL) at 65–75 °C over a period of 3 h. The
solvent was evaporated in vacuo. The residue was purified by col-
umn chromatography (silica gel, hexane–EtOAc, 50:1) to afford
pure 4, which was recrystallized (hexane–EtOAc).
IR (KBr): 1594, 1509, 1441, 1387, 1343 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.38–8.37 (m, 2 H), 8.00–7.98 (m,
1 H), 7.85–7.83 (m, 1 H), 7.72–7.70 (m, 2 H), 7.53–7.46 (m, 9 H).
13C NMR (125 MHz, CDCl3): d = 148.0, 147.5, 141.5, 140.6, 137.6,
132.3, 131.6, 131.3, 130.3, 128.7, 127.8, 127.0, 126.9, 126.8,
126.62, 126.56, 125.8, 123.9.
MS (EI): m/z (%) = 325 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C22H15NO2: 325.1103; found:
325.1107.
1,4-Diphenylnaphthalene (4a)
White solid; mp 136 °C (Lit.2 135–136 °C).
IR (KBr): 1599, 1491, 1446, 1384, 1157 cm–1.
2-Methyl-1,4-diphenylnaphthalene (4f)
White solid; mp 120–121 °C.
IR (KBr): 1589, 1495, 1441, 1387 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.97–7.95 (m, 2 H), 7.54–7.41 (m,
14 H).
13C NMR (125 MHz, CDCl3): d = 141.1, 140.1, 132.2, 130.4, 128.6,
127.5, 126.71, 126.65, 126.1.
1H NMR (500 MHz, CDCl3): d = 7.91–7.89 (m, 1 H), 7.55–7.43 (m,
9 H), 7.37 (s, 1 H), 7.34–7.31 (m, 4 H), 2.26 (s, 3 H).
MS (EI): m/z (%) = 280 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C22H16: 280.1252; found: 280.1246.
13C NMR (125 MHz, CDCl3): d = 141.1, 140.1, 139.7, 138.0, 133.5,
132.9, 130.5, 130.4, 129.9, 128.7, 128.5, 127.5, 127.3, 126.8, 126.1,
125.9, 125.1, 21.1.
MS (EI): m/z (%) = 294 (M+, 100).
1-Phenyl-4-(3-tolyl)naphthalene (4b)
White solid; mp 88–89 °C.
IR (KBr): 1602, 1490, 1442, 1381, 1155 cm–1.
HRMS (EI): m/z [M]+ calcd for C23H18: 294.1409; found: 294.1402.
4-(4-Methoxyphenyl)-2-methyl-1-phenylnaphthalene (4g)
White solid; mp 120–121 °C.
IR (KBr): 1608, 1505, 1463, 1389, 1286, 1244, 1171 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.98–7.95 (m, 2 H), 7.55–7.49 (m,
4 H), 7.46–7.38 (m, 6 H), 7.35–7.33 (m, 2 H), 7.26 (d, J = 7.4 Hz, 1
H), 2.45 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 141.1, 141.0, 140.2, 140.0, 138.2,
132.24, 132.18, 131.1, 130.4, 128.5, 128.4, 128.3, 127.5, 126.75,
126.70, 126.6, 126.05, 126.03, 21.8.
1H NMR (500 MHz, CDCl3): d = 7.92 (d, J = 8.0 Hz, 1 H), 7.52–
7.43 (m, 6 H), 7.35–7.30 (m, 5 H), 7.04 (d, J = 8.5 Hz, 2 H), 3.89 (s,
3 H), 2.25 (s, 3 H).
MS (EI): m/z (%) = 294 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H18: 294.1409; found: 294.1403.
13C NMR (125 MHz, CDCl3): d = 159.2, 140.1, 139.3, 137.8, 133.6,
133.4, 132.9, 131.4, 130.6, 130.5, 129.9, 128.7, 127.3, 126.7, 126.2,
125.9, 125.0, 114.0, 55.6, 21.1.
MS (EI): m/z (%) = 324 (M+, 100).
1-(4-Methoxyphenyl)-4-phenylnaphthalene (4c)
White solid; mp 134–135 °C.
IR (KBr): 1607, 1506, 1442, 1387, 1285, 1241, 1179 cm–1.
HRMS (EI): m/z [M]+ calcd for C24H20O: 324.1514; found:
324.1510.
1H NMR (500 MHz, CDCl3): d = 8.00–7.95 (m, 2 H), 7.55–7.42 (m,
11 H), 7.06–7.05 (m, 2 H), 3.91 (s, 3 H).
4-(4-Bromophenyl)-2-methyl-1-phenylnaphthalene (4h)
White solid; mp 145–146 °C.
IR (KBr): 1599, 1494, 1441, 1389 cm–1.
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Z. Chen et al.
PAPER
1H NMR (500 MHz, CDCl3): d = 7.84–7.82 (m, 1 H), 7.64–7.62 (m,
2 H), 7.53–7.50 (m, 2 H), 7.48–7.40 (m, 4 H), 7.36–7.29 (m, 5 H),
2.26 (s, 3 H).
HRMS (EI): m/z [M]+ calcd for C23H17NO3: 355.1208; found:
355.1206.
1-(2-Methoxyphenyl)-4-phenylnaphthalene (4m)
White solid; mp 131–132 °C.
IR (KBr): 1599, 1488, 1461, 1386, 1285, 1252, 1173 cm–1.
13C NMR (125 MHz, CDCl3): d = 140.0, 139.9, 138.5, 138.3, 133.6,
132.9, 132.0, 131.7, 130.4, 130.1, 129.9, 128.7, 127.4, 126.9, 126.1,
125.8, 125.3, 121.7, 21.0.
MS (EI): m/z (%) = 372 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17Br: 372.0514; found:
1H NMR (500 MHz, CDCl3): d = 7.95–7.93 (m, 1 H), 7.66–7.64 (m,
1 H), 7.55–7.32 (m, 11 H), 7.09–7.05 (m, 2 H), 3.72 (s, 3 H).
372.0510.
13C NMR (125 MHz, CDCl3): d = 157.6, 141.3, 140.0, 136.8, 132.7,
132.3, 131.9, 130.5, 129.9, 129.3, 128.5, 127.4, 127.1, 127.0, 126.8,
126.5, 125.9, 125.7, 120.9, 111.3, 55.9.
1-(4-Methoxyphenyl)-4-(3-tolyl)naphthalene (4i)
White solid; mp 105–106 °C.
IR (KBr): 1605, 1504, 1445, 1387, 1287, 1246, 1171 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.99–7.95 (m, 2 H), 7.46–7.37 (m,
7 H), 7.34–7.32 (m, 2 H), 7.25–7.23 (m, 1 H), 7.05–7.03 (m, 2 H),
3.89 (s, 3 H), 2.45 (s, 3 H).
MS (EI): m/z (%) = 310 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H18O: 310.1358; found:
310.1354.
1-(2-Methoxyphenyl)-4-(3-tolyl)naphthalene (4n)
Colorless oil.
13C NMR (125 MHz, CDCl3): d = 141.1, 139.9, 139.6, 138.1, 133.5,
132.4, 132.3, 131.4, 131.1, 128.4, 128.2, 127.5, 126.72, 126.68,
126.65, 126.0, 55.6, 21.8.
MS (EI): m/z (%) = 324 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C24H20O: 324.1514; found:
IR (KBr): 1602, 1492, 1462, 1386, 1293, 1249, 1181 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.96–7.94 (m, 1 H), 7.64–7.63 (m,
1 H), 7.44–7.34 (m, 9 H), 7.32–7.30 (m, 1 H), 7.07–7.02 (m, 2 H),
3.69 (s, 3 H), 2.43 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 157.5, 141.2, 140.1, 138.0, 136.7,
132.6, 132.3, 131.9, 131.2, 129.9, 129.2, 128.3, 128.1, 127.5, 127.1,
127.0, 126.65, 126.56, 125.8, 125.7, 120.8, 111.2, 55.8, 21.8.
324.1507.
1,4-Bis(4-methoxyphenyl)naphthalene (4j)
White solid; mp 155–156 °C.
IR (KBr): 1609, 1509, 1445, 1383, 1284, 1246, 1175 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.02–8.00 (m, 2 H), 7.49–7.44 (m,
8 H), 7.09–7.06 (m, 4 H), 3.92 (s, 6 H).
MS (EI): m/z (%) = 324 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C24H20O: 324.1514; found:
324.1509.
1-(2-Methoxyphenyl)-4-(4-methoxyphenyl)naphthalene (4o)
White solid; mp 113–114 °C.
IR (KBr): 1598, 1507, 1461, 1387, 1283, 1246, 1176 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.97–7.95 (m, 1 H), 7.64–7.63 (m,
1 H), 7.48–7.31 (m, 8 H), 7.10–7.03 (m, 4 H), 3.88 (s, 3 H), 3.72 (s,
3 H).
13C NMR (125 MHz, CDCl3): d = 159.2, 139.4, 133.5, 132.4, 131.4,
126.74, 126.67, 125.9, 114.0, 55.6.
MS (EI): m/z (%) = 340 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C24H20O2: 340.1463; found:
340.1462.
1-(4-Bromophenyl)-4-(4-methoxyphenyl)naphthalene (4k)
White solid; mp 176–177 °C.
IR (KBr): 1605, 1504, 1458, 1385, 1285, 1242, 1174 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.00–7.98 (m, 1 H), 7.89–7.88 (m,
1 H), 7.63 (d, J = 8.3 Hz, 2 H), 7.46–7.39 (m, 8 H), 7.05 (d, J = 8.6
Hz, 2 H), 3.90 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 159.2, 157.6, 139.7, 136.5, 133.6,
132.7, 132.3, 132.1, 131.5, 129.9, 129.2, 127.1, 127.0, 126.7, 126.5,
125.8, 125.7, 120.9, 114.0, 111.3, 55.9, 55.6.
MS (EI): m/z (%) = 340 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C24H20O2: 340.1463; found:
340.1456.
13C NMR (125 MHz, CDCl3): d = 159.3, 140.2, 140.0, 138.4, 133.2,
132.4, 132.03, 131.96, 131.7, 131.4, 126.8, 126.69, 126.66, 126.3,
126.25, 126.16, 121.7, 55.6.
MS (EI): m/z (%) = 388 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17BrO: 388.0463; found:
1-(4-Bromophenyl)-4-(2-methoxyphenyl)naphthalene (4p)
White solid; mp 124–125 °C.
IR (KBr): 1604, 1491, 1459, 1386, 1296, 1238 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.88–7.86 (m, 1 H), 7.65–7.61 (m,
3 H), 7.43–7.37 (m, 7 H), 7.32–7.30 (m, 1 H), 7.09–7.05 (m, 2 H),
3.72 (s, 3 H).
388.0457.
1-(4-Methoxyphenyl)-4-(4-nitrophenyl)naphthalene (4l)
Yellow solid; mp 160–161 °C.
IR (KBr): 1596, 1514, 1443, 1347, 1288, 1243, 1176 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.41–8.39 (m, 2 H), 8.06–8.05 (m,
1 H), 7.87–7.86 (m, 1 H), 7.74–7.73 (m, 2 H), 7.52–7.47 (m, 6 H),
7.10–7.09 (m, 2 H), 3.94 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 157.5, 140.2, 138.7, 137.3, 132.7,
132.2, 132.1, 131.7, 129.7, 129.4, 127.15, 127.08, 126.7, 126.1,
125.9, 121.7, 120.9, 111.3, 55.9.
MS (EI): m/z (%) = 388 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17BrO: 388.0463; found:
388.0465.
13C NMR (125 MHz, CDCl3): d = 159.4, 148.1, 147.4, 141.2, 137.2,
132.9, 132.4, 131.6, 131.4, 131.2, 127.1, 126.9, 126.7, 126.6, 126.4,
125.7, 123.9, 114.1, 55.6.
1-Phenyl-4-(2-tolyl)naphthalene (4q)
White solid; mp 112–113 °C.
IR (KBr): 1590, 1495, 1440, 1386 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.90–7.88 (m, 1 H), 7.55–7.43 (m,
9 H), 7.37–7.31 (m, 5 H), 2.26 (s, 3 H).
MS (EI): m/z (%) = 355 (M+, 100).
Synthesis 2009, No. 7, 1075–1080 © Thieme Stuttgart · New York

PAPER
One-Pot Synthesis of 1,4-Diarylnaphthalenes
1079
13C NMR (125 MHz, CDCl3): d = 141.1, 140.1, 139.7, 138.1, 133.6,
132.9, 130.5, 130.4, 129.9, 128.7, 128.5, 127.5, 127.3, 126.8, 126.2,
125.9, 125.1, 21.0.
MS (EI): m/z (%) = 294 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H18: 294.1409; found: 294.1405.
hyd THF (25 mL) at 0 °C. The mixture was then stirred at r.t. for 4
h. A suspension of benzenediazonium-2-carboxylate (1, 6 mmol) in
DCE (30 mL) was added dropwise at 70–75 °C over a period of 3
h. The solvent was evaporated in vacuo. The crude product was pu-
rified by column chromatography (silica gel, hexane–EtOAc, 50:1)
and recrystallized (hexane–EtOAc) to afford 7 (85% yield) as a
white solid; mp 80–81 °C.
1-(4-Bromophenyl)-4-(2-tolyl)naphthalene (4r)
White solid; mp 142–143 °C.
IR (KBr): 1599, 1493, 1440, 1388 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.84–7.82 (m, 1 H), 7.64–7.62 (m,
2 H), 7.53–7.40 (m, 6 H), 7.35–7.29 (m, 5 H), 2.25 (s, 3 H).
IR (KBr): 1597, 1489, 1439, 1353, 1284, 1245, 1169 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.31–7.26 (m, 4 H), 7.23–7.18 (m,
2 H), 7.08–7.03 (m, 4 H), 6.96–6.94 (m, 2 H), 6.88–6.85 (m, 1 H),
5.97–5.96 (m, 1 H), 5.92–5.89 (m, 1 H), 5.30–5.28 (m, 1 H), 4.72–
4.70 (m, 1 H), 3.92 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 140.0, 139.9, 138.5, 138.4, 133.6,
132.9, 132.0, 131.7, 130.4, 130.1, 129.9, 128.7, 127.4, 126.9, 126.1,
125.8, 125.3, 121.7, 21.0.
MS (EI): m/z (%) = 372 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17Br: 372.0514; found:
13C NMR (125 MHz, CDCl3): d = 157.1, 146.2, 137.5, 137.3, 134.5,
130.2, 129.74, 129.70, 129.1, 128.8, 127.83, 127.79, 127.6, 126.6,
126.5, 126.4, 121.1, 110.8, 55.8, 45.8, 38.1.
MS (EI): m/z (%) = 312 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H20O: 312.1514; found:
372.0517.
312.1512.
1-(2-Chlorophenyl)-4-(3-tolyl)naphthalene (4s)
White solid; mp 110–111 °C.
IR (KBr): 1603, 1508, 1433, 1386, 1157 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.98 (d, J = 8.0 Hz, 1 H), 7.56–
7.53 (m, 2 H), 7.47–7.46 (m, 1 H), 7.43–7.34 (m, 9 H), 7.26–7.25
(m, 1 H), 2.45 (s, 3 H).
Acknowledgment
The authors thank the National Natural Science Foundation of Chi-
na (No. 20672093) and the Specialized Research Fund for Doctoral
Program of Higher Education (20050335101).
13C NMR (125 MHz, CDCl3): d = 140.91, 140.87, 139.7, 138.1,
137.1, 134.5, 132.5, 132.2, 132.0, 131.2, 129.8, 129.2, 128.4, 128.3,
127.5, 126.91, 126.88, 126.8, 126.4, 126.2, 126.1, 21.8.
MS (EI): m/z (%) = 328 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17Cl: 328.1019; found:
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1-(2-Chlorophenyl)-4-(4-methoxyphenyl)naphthalene (4t)
White solid; mp 100–101 °C.
IR (KBr): 1608, 1514, 1456, 1388, 1281, 1254, 1174 cm–1.
1H NMR (500 MHz, CDCl3): d = 8.00–7.98 (m, 1 H), 7.56–7.52 (m,
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126.51, 126.47, 126.2, 126.1, 114.0, 55.6.
MS (EI): m/z (%) = 344 (M+, 100).
HRMS (EI): m/z [M]+ calcd for C23H17ClO: 344.0968; found:
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1-(4-Bromophenyl)-4-(2-chlorophenyl)naphthalene (4u)
White solid; mp 114–115 °C.
IR (KBr): 1486, 1431, 1386, 1157 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.91–7.89 (m, 1 H), 7.64 (d,
J = 8.3 Hz, 2 H), 7.57–7.54 (m, 2 H), 7.45–7.39 (m, 9 H).
13C NMR (125 MHz, CDCl3): d = 139.9, 139.5, 139.4, 137.6, 134.4,
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HRMS (EI): m/z [M]+ calcd for C22H14BrCl: 391.9967; found:
391.9964.
1-(2-Methoxyphenyl)-4-phenyl-1,4-dihydronaphthalene (7)
2-Methoxycinnamaldehyde (2c, 5 mmol) and dimethyl benzylphos-
phonate (3a, 5 mmol) were dissolved in anhyd THF (20 mL). To the
resulting soln was added dropwise slowly t-BuOK (13 mmol) in an-
Synthesis 2009, No. 7, 1075–1080 © Thieme Stuttgart · New York

1080
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